Vertical batch furnace assembly

ABSTRACT

A vertical batch furnace assembly for processing wafers comprising a cassette handling space, a wafer handling space, and a first wall separating the cassette handling space from the wafer handling space. The wall having a wafer transfer opening. The wafer transfer opening is associated with a cassette carrousel comprising a carrousel stage having a plurality of cassette support surfaces each configured for supporting a wafer cassette. The carrousel stage is rotatable by an actuator around a substantially vertical axis to transfer each cassette support surface to a wafer transfer position in front of the wafer transfer opening and to at least one cassette load/retrieve position, wherein the vertical batch furnace assembly is configured to load or retrieve a wafer cassette on or from a cassette support surface of the carrousel stage which is in the at least one load/retrieve position.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationSer. No. 62/880,850 filed Jul. 31, 2019 titled VERTICAL BATCH FURNACEASSEMBLY, the disclosure of which is hereby incorporated by reference inits entirety.

FIELD OF THE DISCLOSURE

The present disclosure generally relates to a vertical batch furnaceassembly for processing wafer.

BACKGROUND

Vertical batch furnace assemblies for processing wafers comprise acassette handling space, a wafer handling space, and a wall separatingthese two spaces. The wall has a wafer transfer opening provided with acassette door opener device in front of which a wafer transfer positionfor a wafer cassette is provided. The cassette handling space isprovided with cassette handling mechanism which may transport wafercassettes between the wafer transfer position and a cassette storage inwhich the wafer cassettes may be stored. The cassette handling space mayalso be provided with a transfer mechanism to move a wafer cassette fromthe wafer transfer position towards the cassette door opener device, sothat the cassette door opener device may engage the wafer cassette andopen the cassette lid of the wafer cassette. The wafer handling space ofthe vertical batch furnace assembly may also be provided with a waferhandler which may remove wafers from a wafer cassette which is engagedto the cassette door opener device, and transfer those wafers throughthe transfer opening to a wafer boat for applying a treatment in aprocess chamber. After treatment of said wafers the wafer handler mayalso put the wafers back into the wafer cassette which is engaged to thecassette door opener device. The cassette door opener device may releasethe engaged wafer cassette and the transfer mechanism may move the wafercassette back to the wafer transfer position. Subsequently the cassettehandling mechanism may transfer the wafer cassette to the cassettestorage and replace it with another wafer cassette from the cassettestorage.

SUMMARY

This summary is provided to introduce a selection of concepts in asimplified form. These concepts are described in further detail in thedetailed description of example embodiments of the disclosure below.This summary is not intended to identify key features or essentialfeatures of the claimed subject matter, nor is it intended to be used tolimit the scope of the claimed subject matter.

It may be realized that typically multiple wafer cassettes need to beunloaded to fill an entire wafer boat. That during the transporting ofwafer cassettes to and from the wafer transfer position, the waferhandler may be unable to transfer wafers and remains idle. That duringan engagement of a wafer cassette with the cassette door opener device,the cassette handling mechanism may be unable to transport a wafercassette to or from the wafer transfer position and remains idle. Thatthis idle time may be detrimental to the efficiency of the verticalbatch furnace assembly.

Therefore, it may be an object to provide a vertical batch furnaceassembly with improved wafer cassette handling.

To that end, there may be provided a vertical batch furnace assemblyaccording to claim 1. More particularly, there may be provided avertical batch furnace assembly for processing wafers. The verticalbatch furnace assembly may comprise a cassette handling space, a waferhandling space, and a first wall. The first wall may separate thecassette handling space from the wafer handling space and may have atleast one wafer transfer opening. In front of the at least one wafertransfer opening, at a side of the first wall which is directed to thecassette handling space, a wafer transfer position for a wafer cassettemay be provided. The at least one wafer transfer opening may beassociated with at least one cassette carrousel. The at least onecassette carrousel may comprise a carrousel stage which may have aplurality of cassette support surfaces which each may be configured forsupporting a wafer cassette. The carrousel stage may be rotatable by anactuator 31 around a substantially vertical axis to transfer eachcassette support surface to at least one cassette load/retrieveposition, and to the wafer transfer position in front of the wafertransfer opening. The vertical batch furnace assembly may be configuredto load or retrieve a wafer cassette on or from a cassette supportsurface of the carrousel stage which is in the at least one cassetteload/retrieve position.

For purposes of summarizing the invention and the advantages achievedover the prior art, certain objects and advantages of the invention havebeen described herein above. Of course, it is to be understood that notnecessarily all such objects or advantages may be achieved in accordancewith any particular embodiment of the invention. Thus, for example,those skilled in the art will recognize that the invention may beembodied or carried out in a manner that achieves or optimizes oneadvantage or group of advantages as taught or suggested herein withoutnecessarily achieving other objects or advantages as may be taught orsuggested herein.

Various embodiments are claimed in the dependent claims, which will befurther elucidated with reference to an example shown in the figures.The embodiments may be combined or may be applied separate from eachother.

All of these embodiments are intended to be within the scope of theinvention herein disclosed. These and other embodiments will becomereadily apparent to those skilled in the art from the following detaileddescription of certain embodiments having reference to the attachedfigures, the invention not being limited to any particular embodiment(s)disclosed.

BRIEF DESCRIPTION OF THE FIGURES

While the specification concludes with claims particularly pointing outand distinctly claiming what are regarded as embodiments of theinvention, the advantages of embodiments of the disclosure may be morereadily ascertained from the description of certain examples of theembodiments of the disclosure when read in conjunction with theaccompanying drawings, in which:

FIG. 1 shows a top, sectional view of a cassette handling space of anexample of a vertical batch furnace assembly according to thedescription; and

FIG. 2 shows a side, sectional view of the example of FIG. 1 .

DETAILED DESCRIPTION OF THE FIGURES

In this application similar or corresponding features are denoted bysimilar or corresponding reference signs. The description of the variousembodiments is not limited to the example shown in the figures and thereference numbers used in the detailed description and the claims arenot intended to limit the description of the embodiments, but areincluded to elucidate the embodiments by referring to the example shownin the figures.

Although certain embodiments and examples are disclosed below, it willbe understood by those in the art that the invention extends beyond thespecifically disclosed embodiments and/or uses of the invention andobvious modifications and equivalents thereof. Thus, it is intended thatthe scope of the invention disclosed should not be limited by theparticular disclosed embodiments described below. The illustrationspresented herein are not meant to be actual views of any particularmaterial, structure, or device, but are merely idealized representationsthat are used to describe embodiments of the disclosure.

As used herein, the term “wafer” may refer to any underlying material ormaterials that may be used, or upon which, a device, a circuit, or afilm may be formed.

In the most general term the present disclosure may provide a verticalbatch furnace assembly 10 for processing wafers, as illustrated in FIGS.1 and 2 . The vertical batch furnace assembly 10 may comprise a cassettehandling space 12, a wafer handling space 14, and a first wall 16. Thefirst wall 16 may separate the cassette handling space 12 from the waferhandling space 14 and may have at least one wafer transfer opening 18,20. In front of the at least one wafer transfer opening 18, 20, at aside of the first wall 16 which is directed to the cassette handlingspace 12, a wafer transfer position 22, 24 for a wafer cassette 26 maybe provided. The at least one wafer transfer opening 18, 20 may beassociated with at least one cassette carrousel 28, 30. The at least onecassette carrousel 28, 30 may comprise a carrousel stage 32 having aplurality of cassette support surfaces 34 which each may be configuredfor supporting a wafer cassette 26. The carrousel stage 32 may berotatable by an actuator 31 around a substantially vertical axis 36 totransfer each cassette support surface 34 to at least one cassetteload/retrieve position 38, 40, and to the wafer transfer position 22, 24in front of the wafer transfer opening 18, 20. The vertical batchfurnace assembly, in particular a cassette handling mechanism, may beconfigured to load or retrieve a wafer cassette 26 on or from a cassettesupport surface 34 of the carrousel stage 32 which is in the at leastone load/retrieve position 38,40.

By virtue of the at least one cassette carrousel 28, 30 according to thedescription, the position in which the cassette handling mechanism 44,46 places a wafer cassette 26 on the carrousel stage 32, and theposition from which wafers are transferred to the wafer boat, aredifferent positions. This means that the vertical batch furnace assembly10, in particular a wafer handler thereof, may transfer wafers from thewafer cassette 26 which is placed in the wafer transfer position 22, 24,and that the vertical batch furnace assembly 10, in particular acassette handler mechanism 44, 46 thereof, may simultaneously transferanother wafer cassette 26 to the load/retrieve position 38, 40. Openingor closing of wafer cassettes 26 and loading/unloading of the wafers mayonly have to stop whilst the carrousel stage 32 is rotated by theactuator 31. This may be a much smaller time than the time which maytypically be needed to transfer a wafer cassette 26 with a cassettehandling mechanism 44, 46 from the wafer transfer position 22, 24 to thecassette storage and transferring a new wafer cassette 26 vice versa.Thus, this solution may be beneficial relative to a solution in whichthe handling speed of the cassette handling mechanism 44, 46 is simplyincreased. Handling wafer cassettes 26 with high speed may cause allkinds of other problems, such as increased risk of particle releasewhich may lead to a higher rejection percentage of the wafers beingproduced. Such problems may be reduced because the cassette handlingmechanism 44, 46 may transfer a wafer cassette 26 to and/or from thecassette load/retrieve position 38, 40 while at the same time wafers arebeing transferred to the wafer boat. This means that the cassettehandling mechanism 44, 46 may take more time for this transferal andthat the cassette handling mechanism 44, 46 may move relatively slow andthus smoothly. Thus, the cassette handling mechanism 44, 46 may berelatively simple and thus less expensive and wafer cassettes 26 aretransferred smoothly so that the release of particles may be reduced.

Another advantage of this configuration may be that the cassettes, afterthe wafers have been transferred by the wafer handler to the wafer boatfor processing, can be left empty on the carrousel stage(s). So, whenthe next action is to unload a processed wafer boat the empty cassettesare already there on the carrousel stage(s). By leaving the emptycassette(s) on the carrousel stage(s), the “work” to be done by thecassette handler is cut in half because it doesn't have to move andstore empty cassettes. If this is done on two carrousel stages, 6cassettes can be used in this way, which corresponds to a pretty fullboat with 150 wafers.

Yet another advantage is that in the case of filler or dummy wafers thecassette for the filler or dummy wafers can remain on the carrouselstage all the time while the filler wafers transfer between the fillercassette and the boat continuously.

In an embodiment each carrousel stage 32 may comprise three cassettesupport surfaces 34. The at least one cassette load/receive position 38,40 may comprises a first load/retrieve position 38 and a secondload/retrieve position 40. The carrousel stage 32 may be rotatable totransfer each of the three cassette support surfaces 34 to the firstload/retrieve position 38, the second load/retrieve position 40, and thewafer transfer position 22, 24.

By having a first load/retrieve position 38 and a second load/retrieveposition 40, multiple wafer cassettes 26 may be placed on the carrouselstage 32 simultaneously. This may ensure that there is always a wafercassette 26 on the carrousel stage 32 available which may be rotated tothe wafer transfer position 22, 24.

In an embodiment the at least one wafer transfer opening 18, 20comprises a first wafer transfer opening 18 in front of which a firstwafer transfer position 22 is provided, and a second wafer transferopening 20 in front of which a second wafer transfer position 24 isprovided.

The at least one cassette carrousel 28, 30 may comprise a first cassettecarrousel 28 and a second cassette carrousel 30. The first cassettecarrousel 28 may be associated with the first wafer transfer opening 18,and the second cassette carrousel 30 may be associated with the secondwafer transfer opening 20. The first and second cassette carrousels 28,30 may have co-linear vertical axes.

The cassette handling space 12 may comprise a cassette storage 41. Thecassette storage 41 may have a plurality of cassette storage positions42 and may be configured to store a plurality of wafer cassettes 26. Thecassette storage 41 may, for example, comprise a number of racks whicheach have a number of cassette storage positions 42, for example aboveone and another and or next to one another. Alternatively oradditionally, the cassette storage 41 may comprise storage carrouselswith storage carrousel stages on which cassette storage positions 42 areprovided. The first cassette carrousel 28 and the second cassettecarrousel 30 may be vertically spaced apart. The cassette storage 41 maycomprise at least one cassette storage carrousel in between the firstcassette carrousel 28 and the second cassette carrousel 30.

By having a second wafer transfer opening 20 in addition to the firstwafer transfer opening 18, wafers may be transferred trough bothopenings to a wafer boat. This will increase the throughput of thevertical batch furnace assembly and thus its efficiency. By having acassette carrousel 28, 30 associated with each wafer transfer opening18, 20 the advantages of the at least one cassette carrousel 28, 30apply for each transfer opening 18, 20, making the vertical batchfurnace assembly still more efficient. By having cassette storagepositions 42 in between the first cassette carrousel 28 and the secondcassette carrousel 30 optimal use is made of all available space in thecassette handling space 12.

In an embodiment the vertical batch furnace assembly 10 may further beprovided with a blower 57 comprising an elongated, slit-like nozzlesubstantially spanning a height of a cassette lid of a wafer cassette 26when supported on a support surface 34 of the carrousel stage 32 of theat least one cassette carrousel 28, 30. The blower 57 may be configuredto blow a curtain-shaped jet stream of a gas substantially spanning theheight of the cassette lid onto the cassette lid when the at least onecassette carrousel 28, 30 transfers the wafer cassette 26 from the atleast one cassette load/receive position 38, 40 to the wafer transferposition 22, 24. The blower 57 may be provided near the at least onecassette carrousel 28, 30. The blower 57 may be mounted to the firstwall 16.

By blowing the gas onto the cassette lid, any contamination or debris onthe cassette lid may be blown away. By using a jet stream it may beensured that a powerful gust of air reaches the cassette lid, therebyensuring the contamination/debris to be blown away. Because the blower57 blows a curtain-shaped jet stream which substantially spans theheight of the cassette lid, the entire height cassette lid is thusbereft of contamination/debris. When the cassette carrousel 28, 30transfers the wafer cassette 26 from the at least one cassetteload/receive position 38, 40 to the wafer transfer position 22, 24 theentire width of the cassette lid is transported past the blower 57. Thismeans that the blower 57 also blows away contamination/debris across theentire width of the cassette lid.

In an embodiment, the cassette storage 41, which may comprise storageracks and/or storage carrousels, may have 10 to 50 cassette storagepositions 42. The cassette storage 41 may e.g., have at least 40cassette storage positions 42.

Typically about 50 to 250 wafers are needed to fill a wafer boat.Typically there are about 25 wafers stored in a wafer cassette. Thismeans that typically 2 to 10 wafer cassettes are needed to fill onewafer boat. By having at least 40 cassette storage positions 42, enoughwafer cassettes 26 may be stored to fill at least two wafer boats, inparticular approximately four wafer boats. Thus the loading andunloading to and from the cassette handling space 12 can be postponedfor quite some time while the vertical batch furnace is processing thewafers from the cassettes which are stored in the cassette handlingspace 12.

In an embodiment the wafer cassettes 26 may be embodied as front openingunified pods (FOUP's). FOUP's are considered standard enclosures forwafers in the industry. Using FOUP's is advantageous for exchangeabilityof the wafer cassettes between the vertical batch furnace assembly 10and other wafer processing machines.

In an embodiment the vertical batch furnace assembly 10 may furthercomprise at least one cassette in-out port 48, and a cassette handlermechanism 44, 46. The at least one cassette in-out port 48 provides theentrance to and the exit from the vertical batch furnace assembly 10,for the exchange of wafer cassettes between the vertical batch furnaceassembly 10 and the outside world. The at least one cassette in-out port48 may be provided in a second wall 58 bounding the cassette handlingspace 12. The cassette handling mechanism 44, 46 may be configured likethe other cassette handling mechanisms 44, 46 as described above. Thecassette handler mechanism 44, 46 may be configured to transfer wafercassettes 26 to and from the at least one cassette in-out port 48. Sucha cassette handler mechanism 44, 46 may handle all of the wafer cassettetransfers within the cassette handling space 12. This may provide anefficient and cost-effective way to transfer wafer cassettes 26.

In an embodiment, the cassette handling mechanism 44, 46 may comprise afirst cassette handler 44 and a second cassette handler 46. The firstcassette handler 44 may be configured to place a wafer cassette 26 ontoa cassette support surface 34 of the carrousel stage 32 which is in thefirst load/retrieve position 38 and to retrieve the wafer cassette 26from the cassette support surface 34 of the carrousel stage 32 which isin the first load/retrieve position 38. The second cassette handler 46may be configured to place a wafer cassette 26 onto a cassette supportsurface 34 of the carrousel stage 32 which is in the secondload/retrieve position 40 and to retrieve the wafer cassette 26 from thecassette support surface 34 of the carrousel stage 32 which is in thesecond load/retrieve position 40.

Alternatively, both the first cassette handler 44 and the secondcassette handler 46 may be configured to place a wafer cassette 26 ontoa cassette support surface 34 of the carrousel stage 32 which is in thefirst load/retrieve position 38 and to retrieve the wafer cassette 26from the cassette support surface 34 of the carrousel stage 32 which isin the first load/retrieve position 38, as well as to place a wafercassette 26 onto a cassette support surface 34 of the carrousel stage 32which is in the second load/retrieve position 40 and to retrieve thewafer cassette 26 from the cassette support surface 34 of the carrouselstage 32 which is in the second load/retrieve position 40.

Each cassette handler 44, 46 may be provided with a cassette handler arm50, and an elevator mechanism 52 which may be configured to reachcassette storage positions 42 at different vertical heights within thecassette handling space 12.

The elevator mechanism 52 of the first cassette handler 44 and theelevator mechanism 52 of the second cassette handler 46 may be arrangedon or adjacent respectively a third wall 60 and a fourth wall 62 whichbound the cassette handling space 12 on opposite ends.

By having two cassette handlers 44, 46, each associated with the firstor second load/retrieve positions 38, 40, both cassette handlers 44, 46may simultaneously transfer wafer cassettes 26 to and from the at leastone cassette carrousel 28,30. This means that wafer cassettes 26 may betransferred more quickly from the cassette storage 41, which means animprovement of efficiency. By arranging the elevator mechanism 52 of thefirst cassette handler 44 opposite the elevator mechanism 52 of thesecond cassette handler 46, the arms 50 of both cassette handlers 44, 46may cover different parts of the cassette handling space 12. Both mayoperate simultaneously without getting in each other's way. Moreover,both may be equipped with a relatively short arm 50 while, incombination still being able to cover the entire cassette handling space12.

In an embodiment the at least one cassette carrousel 28, 30 may beprovided with a transfer mechanism 54. The transfer mechanism 54 may beconfigured to move a wafer cassette 26 supported on a cassette supportsurface 34 in the wafer transfer position 22, 24 towards and/or awayfrom the first wall 16 having the at least one wafer transfer opening18, 20.

For each wafer transfer opening 18, 20 the vertical batch furnaceassembly 10 may comprise a cassette door opener device 56. The cassettedoor opener device 56 may be arranged on the first wall 16 and may beconfigured to engage a wafer cassette 26 which is being moved towardsthe first wall 16 by the transfer mechanism 54 and to open a cassettedoor of said engaged wafer cassette 26.

The vertical batch furnace assembly 10 may further comprise a waferhandler, a process chamber, and a wafer boat handling device. The waferhandler may be positioned in the wafer handling space 14 and may beconfigured to transfer wafers between a wafer cassette 26 engaged to thecassette opener device 56 and a wafer boat. The process chamber may beconfigured to process wafers accommodated in the wafer boat. The waferboat handling device may be positioned under the process chamber andadjacent the wafer handling space 14. The wafer boat handling device maybe provided with the wafer boat in a wafer boat transfer position, andmay be configured to transport the wafer boat to the process chamber,and to the wafer boat transfer position.

The at least one cassette carrousel 28, 30 may rotate a wafer cassette26 to the wafer transfer position 22, 24 which is in front of the atleast one wafer transfer opening 18, 20. By virtue of the transfermechanism 54 the wafer cassette 26 may be moved towards and/or away fromthe cassette door opener device 56 arranged on the first wall, such thatwafers in the wafer cassette 26 may be loaded to/unloaded from the wafercassette 26 by the wafer handler.

Although illustrative embodiments of the present invention have beendescribed above, in part with reference to the accompanying drawings, itis to be understood that the invention is not limited to theseembodiments. Variations to the disclosed embodiments can be understoodand effected by those skilled in the art in practicing the claimedinvention, from a study of the drawings, the disclosure, and theappended claims.

Reference throughout this specification to “one embodiment” or “anembodiment” means that a particular feature, structure or characteristicdescribed in connection with the embodiment is included in at least oneembodiment of the present invention. Thus, the appearances of thephrases “in one embodiment” or “in an embodiment” in various placesthroughout this description are not necessarily all referring to thesame embodiment.

Furthermore, it is noted that particular features, structures, orcharacteristics of one or more of the various embodiments which aredescribed above may be used implemented independently from one anotherand may be combined in any suitable manner to form new, not explicitlydescribed embodiments. The reference numbers used in the detaileddescription and the claims do not limit the description of theembodiments nor do they limit the claims. The reference numbers aresolely used to clarify.

LEGEND

-   10—vertical batch furnace assembly-   12—cassette handling space-   14—wafer handling space-   16—first wall-   18—first wafer transfer opening-   20—second wafer transfer opening-   22—first wafer transfer position-   24—second wafer transfer position-   26—wafer cassette-   28—first cassette carrousel-   30—second cassette carrousel-   31—actuator-   32—carrousel stage-   34—cassette support surface-   36—vertical axis-   38—first load/retrieve position-   40—second load/retrieve position-   41—cassette storage-   42—cassette storage position-   44—first cassette handler-   46—second cassette handler-   48—cassette in-out port-   50—cassette handler arm-   52—elevator mechanism-   54—transfer mechanism-   56—cassette door opener device-   57—blower-   58—second wall-   60—third wall-   62—fourth wall

The invention claimed is:
 1. A vertical batch furnace assembly forprocessing wafers comprising: a cassette handling space; a waferhandling space; and a first wall separating the cassette handling spacefrom the wafer handling space and having at least one wafer transferopening in front of which, at a side of the first wall which is directedto the cassette handling space, a wafer transfer position for a wafercassette is provided; wherein the at least one wafer transfer opening isassociated with at least one cassette carrousel comprising a carrouselstage having a plurality of cassette support surfaces each configuredfor supporting a wafer cassette, wherein the carrousel stage isrotatable by an actuator around a substantially vertical axis totransfer each cassette support surface to: at least one cassetteload/retrieve position, wherein the vertical batch furnace assembly isconfigured to load or retrieve a wafer cassette on or from a cassettesupport surface of the carrousel stage which is in the at least oneload/retrieve position; and to the wafer transfer position in front ofthe wafer transfer opening wherein the at least one cassette carrouselis provided with a transfer mechanism configured to move a wafercassette supported on a cassette support surface in the wafer transferposition towards and/or away from the first wall having the at least onewafer transfer opening.
 2. The vertical batch furnace assembly accordingto claim 1, wherein each carrousel stage comprises three cassettesupport surfaces, wherein the at least one cassette load/receiveposition comprises a first load/retrieve position and a secondload/retrieve position, wherein the carrousel stage is rotatable totransfer each of the three cassette support surfaces to the firstload/retrieve position, the second load/retrieve position, and the wafertransfer position.
 3. The vertical batch furnace assembly according toclaim 2, provided with a cassette handling mechanism comprising a firstcassette handler and a second cassette handler, wherein the firstcassette handler is configured to place a wafer cassette onto a cassettesupport surface of the carrousel stage which is in the firstload/retrieve position and to retrieve the wafer cassette from thecassette support surface of the carrousel stage which is in the firstload/retrieve position, and wherein the second cassette handler isconfigured to place a wafer cassette onto a cassette support surface ofthe carrousel stage which is in the second load/retrieve position and toretrieve the wafer cassette from the cassette support surface of thecarrousel stage which is in the second load/retrieve position.
 4. Thevertical batch furnace assembly according to claim 3, wherein thecassette handling space comprises a cassette storage having a pluralityof cassette storage positions and configured to store a plurality ofwafer cassettes, and wherein each cassette handler is provided with acassette handler arm, and an elevator mechanism configured to reachcassette storage positions at different vertical heights within thecassette handling space.
 5. The vertical batch furnace assemblyaccording to claim 4, wherein the elevator mechanism of the firstcassette handler and the elevator mechanism of the second cassettehandler are arranged on or adjacent respectively a third wall and afourth wall which bound the cassette handling space on opposite ends. 6.The vertical batch furnace assembly according to claim 2, provided witha cassette handling mechanism comprising a first cassette handler and asecond cassette handler, wherein both the first cassette handler and thesecond cassette handler are configured to place a wafer cassette onto acassette support surface of the carrousel stage which is in the firstload/retrieve position and to retrieve the wafer cassette from thecassette support surface of the carrousel stage which is in the firstload/retrieve position, as well as to place a wafer cassette onto acassette support surface of the carrousel stage which is in the secondload/retrieve position and to retrieve the wafer cassette from thecassette support surface of the carrousel stage which is in the secondload/retrieve position.
 7. The vertical batch furnace assembly accordingto claim 1, wherein the at least one wafer transfer opening comprises afirst wafer transfer opening in front of which a first wafer transferposition is provided, and a second wafer transfer opening in front ofwhich a second wafer transfer position is provided.
 8. The verticalbatch furnace assembly according to claim 7, wherein the at least onecassette carrousel comprises a first cassette carrousel and a secondcassette carrousel, wherein the first cassette carrousel is associatedwith the first wafer transfer opening, and the second cassette carrouselis associated with the second wafer transfer opening, and wherein thefirst and second cassette carrousels have co-linear vertical axes. 9.The vertical batch furnace assembly according to claim 8, wherein thecassette handling space comprises a cassette storage having a pluralityof cassette storage positions and configured to store a plurality ofwafer cassettes, wherein the first cassette carrousel and the secondcassette carrousel are vertically spaced part, and wherein the cassettestorage comprises cassette storage positions in between the firstcassette carrousel and the second cassette carrousel.
 10. The verticalbatch furnace assembly according claim 1, further provided with a blowercomprising an elongated, slit-like nozzle substantially spanning aheight of a cassette lid of a wafer cassette when supported on a supportsurface of the carrousel stage of the at least one cassette carrousel,wherein the blower is configured to blow a curtain-shaped jet stream ofa gas substantially spanning the height of the cassette lid onto thecassette lid when the at least one cassette carrousel transfers thewafer cassette from the at least one cassette load/receive position tothe wafer transfer position.
 11. The vertical batch furnace assemblyaccording to claim 10, wherein the blower is provided near the at leastone cassette carrousel.
 12. The vertical batch furnace assemblyaccording to claim 1, wherein the cassette handling space comprises: acassette storage having a plurality of cassette storage positions andconfigured to store a plurality of wafer cassettes; and a cassettehandling mechanism configured to transfer wafer cassettes within thecassette handling space to and from the cassette storage positions,wherein the cassette storage has 10 to 50 cassette storage positions.13. The vertical batch furnace assembly according to claim 1, whereinthe wafer cassettes are embodied as front opening unified pods (FOUP's).14. The vertical batch furnace assembly according to claim 1, furthercomprising at least one cassette in-out port provided in a second wallbounding the cassette handling space, and a cassette handler mechanismconfigured to transfer wafer cassettes to and from the at least onecassette in-out port.
 15. The vertical batch furnace assembly accordingclaim 1, wherein for each wafer transfer opening the vertical batchfurnace assembly comprises: a cassette door opener device arranged onthe first wall and configured to engage a wafer cassette which is beingmoved towards the first wall by the transfer mechanism and to open acassette door of said engaged wafer cassette.
 16. The vertical batchfurnace assembly according to claim 15, wherein the vertical batchfurnace assembly further comprises: a wafer handler positioned in thewafer handling space and configured to transfer wafers between a wafercassette engaged to the cassette door opener device and a wafer boat; aprocess chamber configured to process wafers accommodated in the waferboat; and a wafer boat handling device positioned under the processchamber and adjacent the wafer handling space, wherein the wafer boathandling device is provided with the wafer boat in a wafer boat transferposition, and is configured to transport the wafer boat to the processchamber, and to the wafer boat transfer position.
 17. The vertical batchfurnace assembly according claim 1, wherein for each wafer transferopening the vertical batch furnace assembly comprises: a cassette dooropener device arranged on the first wall and configured to engage awafer cassette which is being moved towards the first wall by thetransfer mechanism and to open a cassette door of said engaged wafercassette.
 18. A vertical batch furnace assembly for processing waferscomprising: a cassette handling space; a wafer handling space; and afirst wall separating the cassette handling space from the waferhandling space and having at least one wafer transfer opening in frontof which, at a side of the first wall which is directed to the cassettehandling space, a wafer transfer position for a wafer cassette isprovided; wherein the at least one wafer transfer opening is associatedwith at least one cassette carrousel comprising a carrousel stage havinga plurality of cassette support surfaces each configured for supportinga wafer cassette, wherein the carrousel stage is rotatable by anactuator around a substantially vertical axis to transfer each cassettesupport surface to: at least one cassette load/retrieve position,wherein the vertical batch furnace assembly is configured to load orretrieve a wafer cassette on or from a cassette support surface of thecarrousel stage which is in the at least one load/retrieve position; andto the wafer transfer position in front of the wafer transfer opening;wherein each carrousel stage comprises three cassette support surfaces,wherein the at least one cassette load/receive position comprises afirst load/retrieve position and a second load/retrieve position,wherein the carrousel stage is rotatable to transfer each of the threecassette support surfaces to the first load/retrieve position, thesecond load/retrieve position, and the wafer transfer position; whereinin the cassette handling space a first cassette handler and a secondcassette handler are provided, wherein the first cassette handler isconfigured to place a wafer cassette onto a cassette support surface ofthe carrousel stage which is in the first load/retrieve position and toretrieve the wafer cassette from the cassette support surface of thecarrousel stage which is in the first load/retrieve position, andwherein the second cassette handler is configured to place a wafercassette onto a cassette support surface of the carrousel stage which isin the second load/retrieve position and to retrieve the wafer cassettefrom the cassette support surface of the carrousel stage which is in thesecond load/retrieve position.
 19. The vertical batch furnace assemblyaccording to claim 18, wherein the cassette handling space comprises acassette storage having a plurality of cassette storage positions andconfigured to store a plurality of wafer cassettes, and wherein eachcassette handler is provided with a cassette handler arm, and anelevator mechanism configured to reach cassette storage positions atdifferent vertical heights within the cassette handling space.
 20. Thevertical batch furnace assembly according to claim 19, wherein theelevator mechanism of the first cassette handler and the elevatormechanism of the second cassette handler are arranged on or adjacentrespectively a third wall and a fourth wall which bound the cassettehandling space on opposite ends.
 21. A vertical batch furnace assemblyfor processing wafers comprising: a cassette handling space; a waferhandling space; and a first wall separating the cassette handling spacefrom the wafer handling space and having at least one wafer transferopening in front of which, at a side of the first wall which is directedto the cassette handling space, a wafer transfer position for a wafercassette is provided; wherein the at least one wafer transfer opening isassociated with at least one cassette carrousel comprising a carrouselstage having a plurality of cassette support surfaces each configuredfor supporting a wafer cassette, wherein the carrousel stage isrotatable by an actuator around a substantially vertical axis totransfer each cassette support surface to: at least one cassetteload/retrieve position, wherein the vertical batch furnace assembly isconfigured to load or retrieve a wafer cassette on or from a cassettesupport surface of the carrousel stage which is in the at least oneload/retrieve position; and to the wafer transfer position in front ofthe wafer transfer opening; wherein each carrousel stage comprises threecassette support surfaces, wherein the at least one cassetteload/receive position comprises a first load/retrieve position and asecond load/retrieve position, wherein the carrousel stage is rotatableto transfer each of the three cassette support surfaces to the firstload/retrieve position, the second load/retrieve position, and the wafertransfer position; wherein the cassette handling space is provided afirst cassette handler and a second cassette handler, wherein both thefirst cassette handler and the second cassette handler are configured toplace a wafer cassette onto a cassette support surface of the carrouselstage which is in the first load/retrieve position and to retrieve thewafer cassette from the cassette support surface of the carrousel stagewhich is in the first load/retrieve position, as well as to place awafer cassette onto a cassette support surface of the carrousel stagewhich is in the second load/retrieve position and to retrieve the wafercassette from the cassette support surface of the carrousel stage whichis in the second load/retrieve position.
 22. The vertical batch furnaceassembly according to claim 21, wherein the cassette handling spacecomprises a cassette storage having a plurality of cassette storagepositions and configured to store a plurality of wafer cassettes, andwherein each cassette handler is provided with a cassette handler arm,and an elevator mechanism configured to reach cassette storage positionsat different vertical heights within the cassette handling space. 23.The vertical batch furnace assembly according to claim 22, wherein theelevator mechanism of the first cassette handler and the elevatormechanism of the second cassette handler are arranged on or adjacentrespectively a third wall and a fourth wall which bound the cassettehandling space on opposite ends.